This invention relates to a safety system which utilizes a cable tensioner and shock absorber that is of special use for erecting the steel frames of buildings and bridges and provides the worker with a safety lifeline cable to which a safety lanyard can be fastened.
The present invention utilizes the earlier inventions by the same inventor shown in U.S. Pat. Nos. 4,037,824 and 5,029,670 which are incorporated herein by reference.
In working in high places on job sites such as on steel beams during the construction and maintenance of buildings and bridges there is a danger that a worker can fall. If some safety measures are not provided, such falls are quite dangerous and can result in serious injury and even death. The inventor of the present invention has provided a safety measure as shown in his two earlier patents which set forth a system that uses a safety lifeline cable which can serve as both a hand hold as well as a point to which one end of a safety worker's lanyard can be fastened. Thus if the worker inadvertently falls the lanyard and cable will arrest the fall. When a fall was arrested in the previous system, a substantial shock on both the safety system and the worker occurred. Also, the safety cable should be tensioned to a predetermined amount in a convenient manner.
The present invention provides an improved safety system which includes the advantages of the previous safety line arrangement but adds a unique tensioner and shock absorber that permits ready tensioning of the safety lifeline cable to a predetermined amount and also provides a shock absorber in case a worker inadvertently falls to lessen both the shock on the system and the worker when the fall is arrested.
The invention utilizes a system for personal safety for a worker on a construction site that includes a safety lifeline cable supported at a suitable height by safety posts or stanchions with each of the terminal ends of the cable suitably attached to the beams at the construction site. The cable is attached to a special cable tensioner and shock absorber which keeps a tension on the cable of a predetermined amount and absorbs shock to the safety system and to the worker in the event the worker inadvertently falls from a beam. The worker is held to the safety cable by a safety lanyard attached between the worker and the lifeline cable. The safety system is designed that a 300 pound weight can fall six feet and the system would arrest the fall. With the system of the present invention, which includes the unique tensioner and shock absorber, a test of 600 pounds falling six feet has been passed satisfactorily.
The special cable tensioner and shock absorber includes an elongated housing which encloses a coil compression spring. Within the spring is an elastomeric shock absorbing member which in turn surrounds an elongated spring compression rod. The rod extends from one end of the compression spring where it is capped by a square washer that rests on one end of the spring through the compression spring and elastomeric shock absorber and out an opening in one of the end walls of the housing where it can be terminated in the cable system. The other end of the housing is also terminated in the cable system.
When the safety cable is initially installed it is tightened to a predetermined tension. This is brought about by the square metal washer on one end of the compression spring, which is affixed to an end of the compression rod, pushing against the compression spring with the other end of the compression spring being restrained by the end wall of the housing. As tension is applied to the cable and on an end of the compression rod, the square plate moves within the housing until the predetermined tension is achieved. The square plate is prevented from rotating by the shape of the plate against the side walls of the housing. The desired tension is indicated by the edge of the square plate, which is preferably painted in a contrasting color such as yellow, reaches an indicia on the housing that indicates the predetermined tension has been achieved.
In the event a worker accidentally falls, a tension force is placed on the safety cable that exceeds the predetermined tension and this further compresses the coil compression spring until the elastomeric shock absorber is also contacted. The shock absorber which is located within the coils of the spring begins to also compress and absorb the shock loading and as it is compressed it expands in diameter which contacts the inner diameter of the coil compression spring to enhance the shock absorbing resistance to the forces placed on the safety cable. It can be seen that the shock forces placed on the safety cable are first primarily absorbed by the coil compression spring and then the shock absorption is supplemented by the elastomeric shock absorber contained within the compression spring.
In addition to protecting a worker, the present invention also offers some protection to the safety system such as when an I-beam inadvertently falls on the safety lifeline cable.